Shielding shoe for filters



N. G. LEFFLER SHIELDING SHOE FOR FILTERS July 17, 1951 3 Sheets-Sheet 1Filed Aug. 9, 1946 VII'IIIIIII'IIIIII 'IIIIIIIII'IIIIIIIIIIIII JVL'LVGustav Lef/ 'ler i iTTORNEYS July N 1951 N. G. LEFFLER SHIELDING SHOEFOR FILTERS 5 SheetS -Sheet 2 Filed Aug. 9, 1946 INVENTOR WILLS GusZia/V Lef/ 'Ler ATTORNEYS Jufly 117, 119531 N. G. LEFF'LEFQ SHIELDINGSHOE FOR FILTERS Filed. Aug. 9, 1946 zmmgz 5 Sheets-Sheet 5 INVENTORNils Gus td'v Lejfiler ATTORNEYfi Patented July 17, 1 951 UNITED STATESPATENT OFFICE Application August 9, 1946, Serial No. 689,314 In SwedenAugust 14, 1945 23 Claims. 1

The present invention relates to filters of the type embodying a movableperforated filter member adapted to pick up on its one side solids froma suspension and to discharge suspension liquid at its other side afterpassage through the openings thereof under the influence of adifferential pressure between said sides. Such a filter is usually, butnot always, formed as a rotary cylindrical drum the peripheral surfaceof which is perforated and provided with a fine mesh wire fabric forpicking up the solids of the suspension in which the drum is partiallysubmerged, and wherein the differential pressure is produced either byevacuating the interior of the drum or subjecting the outer surfacethereof to a superatmospheric pressure. The invention is especiallyadapted for embodiment in rotary drum filters for picking up solids,such as fibers, powders and granules, from suspensions in liquids and ismore particularly concerned with an improved construction of a shieldingshoe for such filters. It is a further development of the invention Ihave disclosed in my previous application Ser. No. 652,464, filed March6, 1946, for Filter.

As in the case of my previous invention above referred to, the presentinvention has also for its primary object to provide a shield shoe ofthe kind defined which will secure a sufficiently good sealing aroundthat portion of the wire fabric where the taking off takes place. It isanother object so to construct the shoe that it will in a high degree beindependent of variations in said difference in pressure. A furtherobject is to provide a sealing shoe which will close off the take offportion effectively in filter drums even if the drum is not perfectlycircular. An object of the present invention in addition to theaforesaid objects is to provide a sealing shoe the frictional wear ofwhich against the moving filter member will be immaterial.

The invention will now be described more in detail with reference to theaccompanying drawings illustrating various embodiments by which theinvention may be realized in connection with vacuum drums for papermaking but it is to be understood that the invention is not limited tothe features so shown but has to be taken in its broadest scope.

In the drawings, wherein like reference numerals indicate like partsthroughout the several views, Fig. 1 is a cross sectional side elevationof the taking-off portion of a filter drum of the cell-free type and theshielding shoe according to the invention and Fig. 2 is a fragmentaryfront elevation of the shoe of Fig. 1 looking from the right in thelatter figure, the drum being removed and a portion of the shoe beingbroken away to show details of construction. Fig. 3 is a fragmentarycross section of the shoe along the line 3-3 in Fig. 1. Fig. 4 is asectional view similar to Fig. 3 showing an alternative connectionbetween the stationary and the movable parts of the shoe. Figs. 5 to '7show in the same way as Figs. 1 to 3, respectively, another embodimentof the invention and Fig. 8 is a fragmentary cross section showing analternative means for securing the movable part of the shoe to thestationary part. Figs. 9 and 10 show in section and from the outer side,respectively, one embodiment, and Fig. 11 shows in section anotherembodiment, of certain roll supporting means according to the invention.Figs. 12 to 14 show in the same way as Figs. 1 to 3, respectively, athird embodiment of the shoe according to the invention. Fig. 15 is afragmentary cross-sectional view similar to those of Figs. 3, 4, 7, 8,14 and shows a flexible ribbon for securing longitudinal sealing betweenthe stationary and the movable members of the shoe. In these viewscertain of the parts have been broken away or omitted, and others havebeen shown in full instead of in section, in order to simplifyillustration of the invention.

Referring first to Figs. 1 to 3, the filter drum comprises a cylindricperforated support I on the outer surface of which the wire mesh fabric,not shown in the drawings, is applied for taking up the solids suspendedin a slurry of, for instance, cellulose fibers to form therefrom thefiber cake 4. The support or filter member I is mounted in the disc-likeends 2 being rotatably journaled in bearings not shown in the drawings.At the outside of the filtering member the doctor 3 is arranged in theusual way for removing the cake 4 deposited on the filter. The drum isconsidered to rotate in the direction of the arrow at the upper end ofFig. 1 and to be submerged in the fiber slurry 5.

At the place of discharge of the filter, that is at the doctor knife anddownwards to the level of the slurry 5, the shielding shoe is applied.The function of the shoe being to seal off the communication between theinterior of the drum and the outer atmosphere, partly to facilitate theremoval of the cake and partly to prevent air from getting access to theinterior of the drum through the portion of the filter member made nakedat the doctor, the shoe extends beyond this place of discharge at eitherside in the peripheral direction. The shoe is in the axial directionsubstantially coextensive with the filtering member or in other wordswith the foraminous portion thereof. In the drawings the shoe issubmerged in the filtrate below the level 6 but this is not at allnecessary for its satisfactory function. In filter drums where thefiltrate is discharged at a low point in the drum the level of thefiltrate is preferably below the lowermost portion of the shoe.

The sealing member of the shoe comprises The in-thatpart'ofythe'foraminous portionof the";

filter member underlaicl by'the band. embodiment shown in-Figs. 1 to "3the-:band'l is pressed against'sliding'surfaces '22 on the stationarymember Hi" as well as against the filter member. lnorder to minimize thefriction against the sliding-surface-E?grooves (similar to. groove 28inFig. 3), may be made in said surface andbe connectedwiththe pressure'medium' of the chamber through channels in'the material of thestationary member.- Once'the band has been pressed against theslidingsurfaces -22 and the filter member i it will'travel with the" filtermember in sealing engagement with said sliding surfaces. Means forkeeping the bandinapproximate working -pos-ition---for instance a bar Ior perforated pipenear the upper sliding "surface Elf-ought to beprovided so that the band will be putin sealing position upon admittingpressure liquid =to the-pressure chamber, as

through said pipe.

In order, however, to insure proper function-? ing of the band inthe-shoe the band'may be caused to run over guide rolls 8 and 9 and ,ajockey roll said rolls being journaled either directly in the-stationarymember M or in arms In the H, 12 andi-i, respectively whicharein turn"pivoted on the-pins E15; it and H,- respectively,

secured to the" stationary member; The guide rolls 8 and 9 journaledinthe arms! I and 12 r may be pressed against the filter member by meansof the springs i8 and 19; The jockey" roll it is preferably pressedagainst the return part of the-band by means-of the "spring 20 so as tostretch the band.

To the chamber formed byjthe stationary member is and the part of theendless belt";

peripheralsurfaces 23 of thestationary member rendering said pressurechamber-- substantially liquid-tight. When using as pressure medium a;liqu'latsuch as water, an effective water lubrication of the sealingsurfaces will be obtained. It isthen preferred always to keep-the bandwet" on the return-run from-roll 9 to -roll 8. leakage of water into thedrum-from the pressure chamber-is notharmful to the good'func Some "work 'substantiallyas described in connection 4 tioning of the filter,since the vacuum in the drum will not appreciably be influenced thereby.

Sometimes the drum can be irregular, for instance as caused by differenteccentricity of the cross-sections of the drum at different places alongthe axis. For even in this case to secure an effective sealing a portionof the band 7 is left unsupported for some length 24 between the sealingsurfaces of the stationarysmember and the filter member (as shownin'Fig. 3, the band i is unsupported at idbetween the peripheral surface23 of the stationary member and the inner peripheral surface of thefilter member I about groove .Z'l). The embodiment shown in Fig. 4 inwhich the sealing surface 23 of the stationary'member ill stands at aright angle to the filter'member allows a greater movement in the.radial direction of the band relative to the stationary member. In thiscase also the band itself is preferably provided with sealing surfaces'atiright angles ..to, the filter member. In order. to allow theguide'rolls 8 and '9 to fol lowthe" movements required by the irregular filtermember the. arms II and spin'dle'sit of the rollsi By providing theperipheral sealing surfaces '23 of the stationary member It or theimpervious border of the filter membe'rrl or both with peripheralgrooves 27 :and 28;respectively,fcommunicating with the. vacuum in theinterior of thedrum 'byichannels, leak water. is prevented from reachingthe filter cakeld'. The same efiect will be'attained'at the upperaxialsealing surface 22if the latter is provided withja similar groove.

Although 7 the pressure in the space "between the'lower sealing surface22"and the filter member may'"be' considered'to be approximately equalto that outsidethe'filter, that is atmospheric pressure, since thefilter member is here.

free from fiber cake, the pressure may, .however,

at this: place be increased byilsupplying pressure. medium from thepressure chamber or from else-- where. to this space so as to counteracta detrimental. bulging outof the band; Atthe upper sealing surface22such an arrangement is ime practical sinceit would splash the fiber.cake-L but an .extra pressure on the outside surface of the. band isnot .necessary here since the'band moves awayjrom'ithe upper. border of*the stationary.

member: whereas it moves toward thelower border.

Although not shown in the drawing the shoe may be' securedlto astationaryshaft or to spindles in the interior-- (centre) of the drumdirectly or over some support devices.

supply conduit Zhfor pressure medium.=.com-

municates preferablywithlthe'. exterior .of :the.

drum through. this .shaft or spindles.

Among the advantages-of this-embodiment of "the, invention its. simple.design may. be emphasized.-

All. seals between the: band and the filter member as wellasbetween-thebandandthe-sta-v tionary member are obtainedfiwithoutextra devices.The..roll spindlesmay be journaled in "sleeves of plastics.(artificialresin) and a slight wear. of these sleeves .is insignificant.

Figs. 5 to 11 .show... another: embodiment ofthe invention.Theelements'having the. reference numerals I to 2] .Jare arranged andformedand l2 'may'lbe equipped with spherical, bearings 25 for theBysuch means it is possible even during .operation to regulate ormove'the discharge place of the.filter merely by turning said-shaftorspindleswThe 55 with the previous embodiment. The substantiallyliquidtight chamber is, however, here arranged within the'opening formedby the band I and is limited in the peripheral direction of the drum bythe guide rolls 8 and 9. The return part of the band passes thereforeoutside the pressure chamber.

In the radial direction of the drum the pressure chamber is limited bythe wall portion 29 of the stationary member |4. Said wall portion issealed in the peripheral direction against the rotating guide rolls 8and 9. The sealing can be carried out in several different ways, as bymeans of a ribbon of leather or rubber or similar flexible materialsecured (in the same manner as element 57 in Fig. 15) to the inside ofthe wall portion 29 so as to be pressed against the rolls by thepressure medium in the pressure chamber. In the embodiment shown in thedrawing, however, the wall portion 29 is provided at the upper as wellas the lower end with a groove 39 carrying the sealing bar 3|. Thegrooves 3|] communicate through the holes 32 with the pressure medium inthe pressure chamber rendering the bars 3| resiliently pressed againstthe rolls 8 and 9 so that the rolls can move against and from the filtermember without jeopardizing the sealing. The bars 3| may also be pressedagainst the rolls by springs. The seals may be located at any place onthe guide rolls between the parts of the band. The lever arms H and I2may, however, preferably be secured to the statoinary member in suchmanner as to limit to a minimum radial movement of the rolls 8 and 9against the sealing bars 3| during their movement against or from thefilter member.

The seal between the, pressure chamber and the interior of the drum atthe tangent lines between the rolls and the band is obtained by pressingthe rolls, as by springs or weights, against the inner side of the band.The movement is then limited by the filter member.

In the axial direction of the drum the pressure chamber is limited bythe sidewalls 33 (Fig. '7) of the stationary member l4 and the sealingbar 34 which is resiliently movable against the filter member in sealinrelation to said sidewalls 33 and the end surfaces 35 of the rolls 8 and9. The sealing bars 34 are hinged in brackets 38 of the stationarymember by means of the arms 31 pivoted to the bars by the pins 36 and tothe brackets 38 by the pins 39. By this arrangement each bar isresiliently movable against the filter member. In order to secure a goodsealing between the rolls 8 and 9 and the side bars 34 also in case ofirregular shape of the filter member, such as may be caused by a certaineccentricity between the cross-sections of the ends of the drum, inwhich case the end surfaces 35 of the rolls 8 and 9 do not move inparallel to the sidewalls 33, a packing or plate 40 of elastic material,such as rubber, is provided between each of said end surfaces 35 and thecooperating sealing bar 34. For making such a movement feasible thesupporting means for the rolls 8 and 9 have to be designed accordingly.In Fig. 8 one mode of carrying out such an independent movement of theends of the roll is illustrated. In this embodiment the arms II and I2(not shown in Fig. 8) are provided with spindles fitting in the openingsof the sleeves 4| secured to the stationary shafts 42 of the rolls. Incase of a relative movement of the ends of the roll in the radialdirection of the drum the roll moves alittle about said spindles of thearms II and I2.

As already mentioned some leakage of water from the pressure chamber tothe interior of the drum has no detrimental influence. It is thereforepossible to use a labyrinth seal 43 in the rolls consistin of thegrooved rotating disclike end 35 of the roll and a stationary ring 44designed so as to cooperate with said disc-like end 35. By this meansthe wear at these ends 35 of the rolls 8 and 9 is avoided and the wearof the packing 40 is eliminated since the latter will seal between twoelements which are stationary in relation to each other except for aslight movement to and from each other when the ends of the roll movedifferently in the radial direction of the drum. The packing may even befixed to the elements 34 and 44. The elasticity of the packing will thentake up the relative movement between these elements. If the rollcylinder is mounted on the stationary shaft 42 by ball or rollerbearings 66 the labyrinth seal 43 may have a very small clearance.Through a sealing device 45 outside the ball bearing 66 the latter willbe protected against leak water which may come into the end portion ofthe roll. The bearing 66 may, of course, be mounted in brackets asusual.

In the embodiment shown in Figs. 1 to 4 and in that to be describedhereinbelow and shown in Figs. 12 to 15 the entire pressure differenceis taken up by the stationary member 4. In the embodiment according toFigs. 5 to 7, however, a given pressure will be exerted on the guiderolls 8 and 9 which is transferred to the stationary member by thesprings I8 and IS. The pressure of the springs is preferably somewhatgreater than the pressure acting in the opposite direction on the rolls8 and 9 by the pressure medium in the pressure chamber in order to bringabout the sealing between the band and the roll in the peripheraldirection of the drum at the side facin the filter member.

Should, however, the vacuum in the interior of the drum decrease,possibly on account of extraneous operating conditions, the roll will bepressed harder against the band. Due to the fact that the elements inquestion move with the same velocity and practically no frictional wearoccurs, the increased pressure will not be very harmful. The variationof the pressure against the band can, however, be avoided if the guiderolls 8 and 9 are journaled in a U- shaped member or fork 46 on the pins4! as shown in Figs. 9 and 10. The fork should be sealed against theroll. The fork is in turn pivoted on the stationary member by means ofthe pins 48 and arms 48'. By so locating said pins in the peripheraldirection of the drum that the total effective pressures on the surfacesexposed to the pressure medium of the pressure chamber become equal oneither side of the axis of the pins 48, the fork and the roll 8 or 9,respectively, journaled therein will substantially come into balanceindependently of the variations of the vacuum in the interior of thedrum. By in-- creasing the surface of the fork exposed to the pressurechamber relative to that of the roll a constant pressure of the rollwill be obtained against the band. The springs l8 and I9 may in thatcase be dispensed with.

Fig. 11 shows another embodiment of the pivoting of the roll in thestationary member. The sleeves 4| (Fig. 8) of the rolls 8 and 9 arejournalled in the arms 49 which are in turn pivoted on the stationarymember l4 on the spindles 50. The cylinder surface as well as the endsof the able in openings in thes'tationaryimember' M.

Byithi's means :the individual independent movem'entz'of thelbo'thendsuof, a rolLagainst the filter lrn'ember is 'perfect so that the rollwill smoothly follow .the iirregularities of the drum.

Among thezadvantageszof the embodiment described withxreierencetosEigsvdto. 11 the very lowaveanof the (band may bementioned. This :is:dueito' the fact that thezba'nd 'does notseal "againststationarysurfaces. The. sidebars 3' 5 tare, it :is truegin the'drawingshown to be-located inrclose 'contact with the ends of .the band but for:sealing purposes1this=is not2at all v n'e'cessary, :at least not inthe/v'space between the '-rolls and not-1even;at-therolls if the latterare :provided with flanges. at the ends. All sealing'elements between:movable "and stationary members: can be somewhat overdimensionedand arefurthermore cheap-and can be'readily replaced.

ln liigsrm to l5 a third embodiment is shown. The elements having thereference numerals I to 2| and 29 are arranged and formed and workessentially in the same wayas'has been described in connection :with theprevious embodiments with respect =-to elements having same numerals.

The substantially liqu'idtight pressure chamber lSLfllSO in this caselocated within the opening 'formed by the parts of the'ba'nd l.Thesealing barsi fi lat the upper and lowerendsof the wall portion 29 ofthefistationarymember'are, how- -ever, contrar-y to thebarsil oi theprevious embodiment, not :p-laced in contact with the rolls *6 land 9butrthe's'hoe has instead'been designed so that=the bars 'ilsealdirectly'against the inner surface o'f-the band T'IIBELYthBFIOHSvhand 9. "By

thismea'ns sealin lagainst thecylindricsurface and-the end of 'the rollisavoided. -In order to reduce the wear of the band the sealing bars maybe replaced by smalldiameter rolls rotating in contact with theband andbeing sealed against the stationarymember. The sealing side bars 55limit together with the side wall 56 of the stationary member M theextension of the lplSSllIB chamber in thevaxial direction of the drum.The bars '55 are resiliently movable against the inner surface of thedrum inthe sameway-as-the sealing bar34 of the preceding embodiment.JIn'Fi'g. l5 anotherembodiment of the sealing in the axial direction hasbeen illustrated. A, flexible sealing ribbon :57 made of, for instance,leather -or rubber is here secured to the sidewall 56 i the stationarymein'ber I 4 and is :pressed against the band i or against the end 20the filter memberzoutside the band by the-pressuremedium.

Among the advantages "of the last described embodiment the simpleexecution of the seals -:may be emphasized.

Since, for the contemplated function of the shoe, sealing isrequiredflagainst the filter member only around the circumference of thecontacting portionof the shoe, the band according to'the presentinvention may be replaced by one comparatively narrow belt at each .endof the rolls. The rolls should then be provided with a suitable sealingmeans, such as a coating or cover of rubber, betweensaid belts and incontact with the filter member; Thefsealing member being -now opentowards the filter member a vapourous :pressure medium must be used inthe pressure chamber formed-in the shoe. In

its inside :surfacebetween the rolls. apur-pose boxes may be usedhaving. slots in the filter i member. rolls I disclosed may be driven byspecial driving means, such as chains or belts, which'm ay be order to:bring about the sealin required be'- tween the belts andthe'filter'member ea'chrbelt has to be provided with a. pressing deviceI along For this walls facingithefbelts and inlets for a ga'seous' orliquid pressure medium to work on the belts through saidslots.

It is, of 'course,-pos'sibl'e to a'certain extent to combine the varioussealing means'described in connection with the different embodiments.

At places where only minor reciprocating movements :occur the sealingelements may be nixed to the' members moving in relation to each other,

the elasticity of the' sealing means then-rendering the movementpossible.

The invention hasinow been described with reference to some differentembodiments but it is to be understood that 'it is -not limited to theseembodiments or the special details shown and described. -In addition tovarious combinations of the-embodiments also quite dififer entembodiments may comeinto question. Thustwo or more shoes of the presentkind may be arranged one after the othera'nd bepr'ovid'ed with a commoncase "kept in liquid tight relation to the Furthermore one ormore of thedriven by the shaft in the centre or thedru'm. In case thedrumdsarrange'cl' 'for interior feed and the shielding shoe therefore isprovided on the outer side of the drum, the driving of the-rolls can, ofcourse, be easily performed. Employed with cell filters in which thecells -open at the one or both ends or" the drum the'shoeof-theinvention will be placed over 'an appropriate number of such cellopenings at the endof-endsof the drum. Although particularly describedconnection with filter Jdrums submerged in a suspension of fiber it isto be understood that 'theinvention can be employed equallywell'i'nconjunction with other types of picking up machines forsuspended solids where theseare picked upon ,a foraminous member by theaction of a pressure difference-between opposite sides of the'foramin-'ousmember.

As used in the .:speciflcation-and claims "hereof,

:the words seal and sealing are not intended to apply:solelyztoiconditions'in which a perfect zsealtis efiected,-becauseifricti'on'al sea-ls are seldom,

ever, absoiutely air-tight or watertight. In-

stead, these Words should be interpreted to mean :that the leakage ofair, water or other fluid is inhibited to the maximum degree practicablein structures of the character described, and that where the seal ismade by frictional engage- -ment. between relatively movable members, a

limited amount of leakage may exist without seriously impairing theutility of the invention.

Vilhat is claime'dds:

A sliie'lding shoe for filters of the type embodyinga movable perforatedfilter member adapted to pick up o'h "its one side solids from asuspensionandto d'ischar-ge suspension liquid at its other side afterpassage through the openings thereof under the iniluenceof adifierential pressure between said sides, said shoe comprisingsupporting said endless-flexible -member for movement relative to saidstationary shoe member and with said perforated filter member, saidstationary shoe member including walls forming a chamber having an openside facing said perforated filter member, means including said endlessflexible member for closing the open side of said chamber and renderingthe latter substantially liquidtight, and mean for supplying fluid underpressure to said chamber for pressing said endless flexible member intocontact with said perforated member.

2. A shielding shoe as claimed in claim 1 wherein at least one end ofsaid stationary shoe member is provided with a supporting surface overwhich said endless member passes in sliding engagement, and whichincludes means for maintaining said endless member in approximateworking position adjacent said surface.

3. A shielding shoe as claimed in claim 2 including grooves in saidsupporting surface communicating with said chamber. 4. A shielding shoeas claimed in claim 1 including at least one roll about which saidendless member is movable, said roll being disposed adjacent the rearend of said stationary shoe member as viewed in the direction ofmovement of said endless member.

5. A shielding shoe for filters of the type embodying a movableperforated filter member adapted to pick up on its one side solids froma suspension and to discharge suspension liquid at its other side afterpassage through the openings thereof under the influence of adifferential pressure between said sides, said shoe comprising a rigidstationary shoe member and a movable sealing shoe member, said movablesealing shoe member comprising two rolls disposed one at each end ofsaid stationary shoe member and an endless flexible band of imperviousmaterial movable about said two rolls and adapted to contact and seal aportion of said perforated filter member and to move revolvinglytherewith, means for rotatably supporting said rolls from saidstationary shoe member, said means being so constructed and arrangedthat at least one of said rolls is movable relatively to said stationaryshoe member toward and away from said perforated filter member, saidstationary shoe member including walls forming a chamber having an openside facing said perforated filter member, means including said endlessflexible band for closing the open side of said chamber and renderingthe latter substantially liquidtight, and means for supplying fluidunder pressure to said chamber for pressing said endless flexible bandinto contact with said perforated filter member.

6. A shielding shoe as claimed in claim 5 wherein said roll supportingmeans includes an arm pivotally mounted on said stationary shoe member,and. means for rotatably journalling said movable roll in said arm.

'7. A shielding shoe as claimed in claim 5 including at least oneadditional roll in contact with said endless band, adjustable means forrotatably supporting said roll from said stationary shoe member, andyieldable means for urging said roll in such direction as to stretchsaid band.

8. A shielding shoe for filters of the type embodying a movableperforated filter member adapted to pick up on its one side solids froma suspension and to discharge suspension liquid at its other side afterpassage through the openings thereof under the influence of adifferential pressure between said sides, said shoe comprising a rigidstationary shoe member, and a sealing shoe member at least a part ofwhich is movable relative to said stationary shoe member, said sealingshoe member comprising a pair of rolls, one at each end of saidstationary member, and an endless flexible member of impervious materialmovable about said rolls, said endless member having a contactingportion movable along with and, at least for the greater portion of itslength, in contact with said movable filter member and a return portion,said stationary shoe member including walls forming a chamber having anopen side facing said movable filter member, and means including thecontacting portion of said endless member for closing the open side ofsaid chamber and rendering the latter substantially liquidtight.

9. A shielding shoe as claimed in claim 8 wherein the return portion ofsaid endless flexible member is within said chamber.

10. A shielding shoe for filters of the type embodying a movableperforated filter member adapted to pick up on its one side solids froma suspension and to discharge suspension liquid at its other side afterpassage through the openings thereof under the influence of adifferential pressure between said sides, said shoe comprising a rigidstationary shoe member, a pair of rolls substantially parallel to oneanother, and an endless flexible member of impervious material movableabout said rolls, said stationary shoe member including a wall portionspaced from and generally parallel to said movable filter member,located between said rolls and in substantially liquidtight contacttherewith, said endless member having a portion between said rollsgenerally parallel to said wall portion movable along with and, at leastfor the greater portion of its length, in contact with said movablefilter element, and means including, said wall portion of the stationaryshoe member, said rolls and the filter contacting portion of saidendless member forming the enclosure of a substantially liquidtightchamber.

11. A sealing shoe as claimed in claim 10 including a pair of sealingbars extending between said rolls at the ends thereof and yieldablymovable toward said movable filter member, said sealing bars havingsubstantially liquidtight contact with said rolls and said stationaryshoe member.

12. A shielding shoe for filters of the type embodying a movableperforated filter member adapted to pick up on its one side solids froma suspension and to discharge suspension liquid at its other side afterpassage through the openings thereof under the influence of adifferential pressure between said sides, said shoe comprising a rigidstationary shoe member, an endless flexible member of imperviousmaterial revolvingly movable relative to said stationary shoe member andhaving a portion spaced from said stationary shoe member and adapted tocontact.

a portion of said movable filter member, sealing means between saidstationary shoe member and the inside surface of said endless member atthe ends of said stationary shoe member in the direc-' tion of movementof said endless member, means including said stationary shoe member andthe portion of said endless member between said sealing means formingthe enclosure of a substantially liquidtight chamber, and a conduitleading to said chamber.

13. A shielding shoe as claimed in claim 1 including at least one rollrotatably supported by said stationary shoe member and about which 2&5 613282;

said-endlessflexible member-is movable, the-ends.- ofjsaid'lroll being.independently: movable toward and away from said filter member.

14-.-..A shielding shoe.= for filters of the type embodying afilter-member comprising. aspere forated portion surrounded by animperviousframeportion and being adaptedto pick p on its--one side:solids froma suspensionand to dis-. charge suspension liquid at itsother sideafter passage through the openings thereof under theinfluence-of a diiferential pressure between. said sides, said shoecomprising-a rigid stationary shoe member having a sidewall generallyparallel to said filter member, end:- wallsperpendicularto said-sidewalland an open side-facing saidrfilter member, an endless band ofimpervious material movable relative to said stationary shoe member. andclosing theside thereof facing. said. filter member exceptrforrelatively narrow spacesbetweenthe end walls of said stationary shoemember and the edges of said-endless band, pertions-of said endlessbandadjacent its edges-being. in contact with the impervious frameportionof. saidfilter member, and means'forsealing said spaces, saidsealing-means.being:-. so constructed andarranged as to maintain-theseal While per.--

member, into frictional engagement: with said.-

impervious-frame portion.

16. A shielding-shoe as: claimed. in claim. 15. wherein-saidisealingbaris provided with-asun-v face perpendicular to saidband'and in slidingengagement with the'edge thereof i 17.'A shielding shoe. asclaimedinclaim 14.

wherein a said sealing, means comprises va. flexible sealing ribbonfixed to eachv end wall, of said, stationary= shoe member and soconstructed and. arranged that one of its surfacesis-inicontact.

with r the; portion: of said endless band. adjacent said endwalli.

18..-.A sealing shoe as claimed. inv claimkl.

wherein said sealing means comprisesasurface on said stationary shoememberparallel to and ill-Sliding contactwithithe marginalportion of.said band, said band having an unsupported pore tion between :theportions thereof in contact with saidrimpervious frame portion andsaidsurface.

19, A shielding shoe as claimed inclaim 18. wherein atleast one oftheportions. of saidime pervious frame. portion and said surface incontact with-said endless band is provided witha.

groove communicating with asourceofvacuump 20. A shielding shoe forfilters of the. type em-:- bodying a movable perforated filter member.

adapted topick up. on itsonesidesolids from. a suspension and to,discharge suspensionliquid.

1'2 less member having; :a-contaeting portion movable along: with and,at lleastfor the. greatest portion' of-its? length; in contact: withsaid movablefilter member and a return portion; said stationaryshoe'memberincluding wallsv forminga-chamber havingian, open side facingsaid movablefilter member, means including the portionof said endlessmember inpcontactwith said movable-filter member for closing-theopenside ofsaidchamber and rendering the latter: sub stantially liquidtight,means fonsupplying a fluid underpressure to said .-chamb'er,qand meansoutside saidc-hamber for supplying liquid under-pres sure-to thecoil-tasting portion of; said endless:

member.

21. A shielding. shoe as claimed in' claim 1' includingat least onefeeder; roll about which said endless flexible member.- is; movable.-

22.- A shielding shoe as claimed in claim: 1

including-a flexible sealing ribbon fixed to saidstationary shoe memberand so-constructed and arranged: that one. of 1 its .sides :ismaintainedin sealing contact with said endless-flexible member byr'the pressure insaidchamber.

23. A shieldingshoe for filters of the: type embodymg afilter membercomprising i a perforated portion surrounded by an impervious .frameipoztionv and being adapted to pickup on it'sone side solids; from a;suspension and to discharge suspension liquid at itsother side afterpassage through theopenings thereof under theinfiuence' ofardifierential pressure between said sides, said shoe comprising a rigidstationary shoe memberhaving a, side: wall generally parallel :to said--filter member and end walls perpendicular-tosaid side' Wall forming-'achamber having an openside fac-' ing saidfiltermemher, an-rendless bandof impervious: materialmov-able'relative to said stationary. shoememberand having portions adj acent. its; edges in contact with theimperviousframe portion of said filter member; saidbandand: imperviousframeportion closing the openside-of. said chamberexcept' for relativelymarrow spaces between theend walls of said' sta-l tionary shoe-memberand said impervious frame portion, and-means for'sealing said-spaces-torendersaidchamber substantially liquidtight;

said meanso-being so-constructed and-arrangedas to. maintain the seal=while permitting rotary movement-of said impervious=f-rame portionrelative to saidstationary shoe member.

N ILS-GUSTAV LEFFLER;

REFERENCES CITED The-following references are ofrecord' in the file ofthis-patent:

UNITED STATES PATENTS

